Hello I am new to this site, After a few weeks of looking around on different site's for my problem and coming up with nothing, I have had to become a member for some experienced wise words!! The car in question is a l322 hse from 2009 with the tdv8 engine
BUT i was driving the car the other week and the temp gauge shot up to over heating for the first time since owning the car. I turned the car off straight away and let it cool down. when i checked the coolant level it was empty i was wondering where it had all gone and i originally thought head gasket as there was no leaks from under the car. I filled the car up and got it to a garage and it didnt over heat but lost some coolant.

Once at the garage he filled and bled the cooling system but I am getting water flow back through the return pipe into my expansion tank which looks like bubbles which worried us more to head gasket. He pressure tested the system sniff tested and all come back normal so he was happy it isnt the head. I then fitted a new housing which includes the temp sensor and thermostat in case this was causing an affect on the system,
I bled the car back up following a procedure i found on one of the forums it was all looking fine with still a return flow from my top pipe into expansion tank it held its coolant on the drive up to temp and produced warm air out the heater indicating it was flowing round the system correctly telling my the water pump is working correctly. so this is where my problem is when cold my car is telling me it has sufficient coolant fluid level just under max. when i start the car its stays at that lever for a short period of time than then disappears pretty quick i am guessing when the thermostat opens.

The top hose for the radiator is pressuring the return pipe is flowing into the empty expansion tank and telling me low coolant on the dash, which there is no coolant in the tank between min and max I can just see a bit at the bottom. when i turn the engine off and let it cool down the expansion tank gradually gets the coolant level back to the correct level just under max once it is at a certain temperature. Why is this happening? what would cause it? anything i could look at doing?

Any information will be appreciated

Sounds like you still have air in the system.

i had all but same on a 4ltr p38 and it was the water pump cavatating causing air in the system i replaced it and all was good new vehicle purchase
2007 supercharged 4.2 java black .sand leather vogue se trim
previous cars .
range rover classic 200 tdi
discovery 1 200 tdi
freelander 2 2008 hse
discovery 1 300 tdi
p38 4.0 ltr man r380 ex royal support vehicle on v5c
discovery td5 man off roader